Flying Above Mount Olympus

The European orbiter, Mars Express, took a close-up stereo view from overhead of the summit crater at Olympus Mons, the highest volcano in our Solar System.

Olympus Mons has an average elevation of 22 km (13 miles) and the caldera (or summit crater) has a depth of about 3 km (1.8 miles). This is the first high-resolution color image of the complete caldera of Olympus Mons.

Olympus Mons is the largest volcano in the solar system, towering many times over Mt. Everest. The view is centered at 18.3°N and 227°E. The image is about 102 km (60 miles) across with a resolution of 12 meters per pixel. South is at the top. Credit:ESA Mars Express

The image was taken from a height of 273 km (160 miles) during orbit 37 by the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express on January 21, 2004.

A complementary three-dimensional view shows the Olympus Mons volcano in its entirety, to put the caldera images in context. It has been derived from the Mars Orbiter Laser Altimeter (MOLA) topographic data superimposed with the Mars Orbiter Camera (MOC) wide-angle image mosaic.

Banner details of the caldera in perspective from Mars Express shows the southern summit. The image has been calculated from the digital elevation model derived from the stereo channels and combined with the nadir- and color-channels of the Mars Express HRSC.

Such oblique views, resembling how a person looking out a window might view across the broad Martian horizon, have a special appeal, according to Dr. Bill Hartmann, a member of the other imaging team that works with the Mars Global Surveyor. " There are a number of regions I’d like to see photographed in that ‘human’ oblique view angle, the way we are used to seeing the land from our airplane windows. I think that they inspire a broader, more holistic view that lets us see Mars in the context of our terrestrial experience (not as an alien "target"), and that in turn inspires new thinking, a new sense of relationships, and new questions."

The Olympus scene reveals tongue-shaped mass-movement features in three-dimensions on the southern wall. The striations are tectonic faults. After lava production has ceased the caldera collapsed over the emptied magma chamber.

Through the collapse the surface suffers from extension and so extensional fractures are formed. The elevation level on which these fractures can be observed represents the event of the oldest caldera collapse.

Later lava production has produced new caldera collapses at different locations (the other circular depressions), they partly destroyed the circular fracture pattern of the oldest one.

University of Buffalo volcanologist, Dr. Tracy Gregg, discussed the scientific appeal of studying Martian volcanoes in detail. "If both of these [Opportunity and Spirit] landers survive with airbag technology, then it blows the doors wide open for future Mars landing sites with far more interesting terrain. A landing site near a volcano might be possible, now that the airbag technology has worked so wonderfully."

The current generation of Mars missions has adopted the theme, "Follow the Water", as a quest to understand the complex geological history of a planet that may have had significant reserves once. For that much warmer and wetter Mars, this motto also requires other ingredients for microbial life, including primordial "fire" in the form of biological temperature ranges and potentially geothermal heat.

"I’d like to see us land ON a volcano," said Gregg. "Right on the flanks. Often the best place to look for evidence of life on any planet is near volcanoes."

"That may sound counterintuitive, but think about Yellowstone National Park , which really is nothing but a huge volcano," said Gregg. "Even when the weather in Wyoming is 20 below zero, all the geysers, which are fed by volcanic heat, are swarming with bacteria and all kinds of happy little things cruising around in the water. So, since we think that the necessary ingredients for life on earth were water and heat, we are looking for the same things on Mars, and while we definitely have evidence of water there, we still are looking for a source of heat."

While Olympus Mons is inactive, volcanologists are not entirely convinced more isn’t going on geothermally on Mars. "If you’d asked me [if there were not active surface volcanoes] 10 years ago–or even 5–I might’ve said yes," said Gregg. "Now I’m not so sure."

On Mars, "where would I look for recent volcanic activity? Depends on how you want to define it on Mars," said Gregg. "I strongly suspect there are still molten (or at least mushy) magma bodies beneath the huge Tharsis volcanoes , and beneath Elysium Mons ."

"But the youngest surficial activity discovered to date (and it’s probably 1 million years old, which would be considered quite young, and possibly ‘active’ on Mars) is in a region that contains no large volcanic structures of any kind," said Gregg. "Instead, there are cracks in the ground, and a few low-lying volcanoes that can’t even be seen except in the high-resolution topography (they are too subtle for imagery to reveal). This area is called Cerberus Fossae ."

"I’d love to see obliques looking down Valles Marineris, across some of the big frosty craters, across some of the lava flows, down big riverbed channels like Ares Vallis and Ma’adim Vallis, and so on", concluded Hartmann.